Submitted to: Virology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/20/2009
Publication Date: 12/20/2009
Citation: Drechsler, Y., Bohls, R.L., Smith, R., Silvy, N., Lillehoj, H.S., Collisson, E. 2009. An avian, oncogenic retrovirus replicates in vivo in more than 50% of CD4+ and CD8+ T lymphocytes from an endangered grouse. Virology. (83)380-386. Interpretive Summary: Reticuloendotheliosis virus (REV), an avian oncogenic retrovirus REV are a group of viruses in the family Retroviridae, infect praire chickens in the captive breeding flock and this virus has been associated with acute cell neoplasia, runting disease, and chronic cell neoplasia of lymphoid and other tissues. A major obstacle to breeding the Attwater's prairie chicken (APC) has been the recurring emergence of REV. REV has been suggested to be immunosuppressive. Currently, nothing is known of the cellular immune system or the pathogenesis of REV in prairie chickens, including the role of cellular immunity in controlling viral infection. Critical to the avian immune response to viral infection, chicken T lymphocytes have been shown to control antigen specific control of viral infection. Direct infection could functionally affect cells of the immune system and explain the immunosuppressive nature of REV. The alterations in phenotype of lymphocytes could be associated directly with infection or indirectly, as a result of immune stimulation of CD8+ T lymphocytes. In this study, Western University of Health Sciences collaborated with ARS scientists to find that a decrease in CD8+ cells was associated with wasting of REV-infected birds suggesting an association of decreased T-cell subset with immunosuppression. This finding is important to understand the immune suppression mechanism mediated by REV infection. This new knowledge will help in the designing strategy against REV infection in APC.
Technical Abstract: Reoccurring infection of reticuloendotheliosis virus (REV), an avian oncogenic retrovirus, has been a major obstacle in attempts to breed and release an endangered grouse, the Attwater's prairie chicken (Tympanicus cupido attwateri). REV infection of these birds in breeding facilities was found to result in significant decreases in the CD4+ and increases in the CD8+ lymphocyte populations, although experimental infection of birds resulted in only increases in the CD8+ lymphocytes. Because our indirect immunofluorescent assay readily detected infection of both CD4+ and CD8+ lymphocytes, a triple labeling flow cytometric procedure was developed to quantify the individual lymphocytes infected in vivo with REV. Lymphocytes were gated with a biotinylated pan-leukocyte marker bound to streptavidin R-PE-Cy5. Chicken CD4 or CD8 specific mouse MAb directly labeled with R-PE identified the phenotype and with permeabilizing of cells, infection was indirectly labeled with rabbit IgG specific for the REV gag polypeptide and FITC conjugated goat anti-rabbit antibody. More than 50% of the total lymphocytes and of the total CD4+ or CD8+ lymphocytes supported in vivo viral expression in all infected birds examined. Remarkably, this level of infection was detected in the absence of visible clinical signs of illness.